According to the EP 0248987 B 1, an upgrading method for volatile compounds has become known, according to which the enrichment of volatile compounds from liquid and solid substances containing said volatile compounds is possible in a closed system without using any auxiliary substances if it is carried through by heating the basic material at elevated temperatures and condensing the volatile substances at lower temperatures in a system which consists of an evaporator- and condensing vessel as well as a capillary tube connecting said vessels and having an inside diameter of less than 1 mm. The method according to the EP 0248987 B1 did allow an enrichment of the volatile substances in the condensate which had not been known before. For this purpose, however, a relatively high expenditure of time had been necessary.